An MOF-tailored hierarchical porous microenvironment for CO2 as an efficient filler for mixed matrix membranes

• An MOF achieved adjustable hierarchical pores and favorable microenvironment for CO 2 . • The MOF-Cu@Al(bpydc) accelerates the diffusion and solubility of CO 2 in the MMMs. • The final MMMs exhibit superior CO 2 /CH 4 separation performance. • Cu@Al(bpydc) provides an alternative avenue for designing excellent MOF-based MMM. Mixed matrix membranes (MMMs) for separating CO 2 /CH 4 mixture were prepared through incorporating Cu@Al(bpydc) into a Pebax polymer in which Cu@Al(bpydc) synthesized through a competitive coordination method achieved a controllable micro/mesopores structure and abundant functional sites for CO 2 . The hierarchical pores of Cu@Al(bpydc) provided multidimensional diffusion channels in the Pebax matrix, which increased the diffusion of CO 2 . In addition, the abundant chemical groups, such as the polar group COO – and nitrogen Lewis basic groups, created a microenvironment with multiple CO 2 affinity sites in the membrane, increasing the selectivity of CO 2 . A MMM loaded with 5 wt% Cu@Al(bpydc) exhibited excellent CO 2 separating property under wet mixed-gas test conditions. In particular, the CO 2 permeability and selectivity of the MMMs were increased by 92.90% and 27.10% respectively, compared with those of pure Pebax, showing exceptional potential for the separation and capture of CO 2 from biological natural gas.